The bonus cache is not at the posted coordinates.
This is a bonus cache to the Leque Island Estuary Adventure Lab
Inorder to find and log this Bonus Cache you must first complete the 5 Adventure Lab locations and obtain the clues to this bonus location in the journals from each Lab location.
Cache is at N48 AB.CDE W122 FG.HIJ
WARNING: When coming from Stanwood on State Route 532 DO NOT attempt to turn left into Leque Island Estuary crossing the double yellow lines, instead continue west and turn left at Smith Road make a U-turn and head east on 532 turning right into the Estuary avoiding a possible ticket!
Congratulations to msaxby on FTF!